The ion exchange membrane method electrolysis industry represented by the alkali chloride electrolysis plays an important role as a primary material industry. In this electrolysis industry, the ion exchange membrane method electrolytic cell (hereinafter referred to as “electrolytic cell” when appropriate) forms a technical core.
For example, a co-applicant of the present invention has provided an electrolytic cell in patent document 1 wherein a corrugated partition at the anode side and a corrugated partition at the cathode side, which are capable of being fitted with each other to form superposed corrugated partition layers having a ridge-and-groove configuration, and electrode plates are fitted onto the ridge portions of the partition layers; and the groove portions extend vertically not in one long straight line, and each groove portion is placed in contact with the adjacent groove portions in a liquid mixing region. In this electrolytic cell, liquid electrolyte flows upwardly due to the action of electrolyte bubbles generated by electrolysis while the liquid electrolyte is mixed in the liquid mixing regions, whereby the distribution of concentration of liquid electrolyte becomes uniform and thus the electrolysis operation can be stably continued over a long period of time.
In another electrolyte cell, proposed in, for example, patent document 2, a cathode is placed in contact with an ion exchange membrane by comb-like leaf spring members whereby damage of the ion exchange membrane can be avoided
As a modification of the ion exchange membrane method electrolytic cell, an electrolyte cell is proposed in, for example, patent document 3, which has a structure such that leaf spring members are supported by a leaf-spring retaining member whereby the stress applied between the electrode and the ion exchange membrane are rendered small and consequently damage of the ion exchange membrane is minimized.
The above-mentioned modified ion exchange membrane method electrolytic cell has a problem such that the leaf spring-retaining member is apt to be distorted in operation by the pressure whereby the ion exchange membrane is occasionally spaced away from the cathode which leads to increase in the electrolysis voltage. When the electrolytic cell apparatus is disassembled and again assembled, height of the leaf spring-retaining member must be adjusted.
Therefore, an improved ion exchange membrane method electrolytic cell is desired wherein another flexible cushion is interposed between the cathode and the ion exchange membrane to minimize the damage of the ion exchange membrane and the deformation of the cushion due to the stress by the pressure.
Zero gap-type ion exchange membrane method electrolytic cells have been proposed in, for example, patent documents 4 to 6 wherein a cushion matt is placed between an electrically conductive plate and an electrode. In these proposed electrolytic cells, the electrically conductive plate is made of a rigid mesh screen, i.e., a perforated plate.
As seen from the above explanation, in the conventional ion exchange membrane method electrolytic cells wherein the electrically conductive plate is spaced apart from the partition at a predetermined distance and a cushion mat is arranged between the electrically conductive plate and the electrode, it is usual that the electrically conductive plate is made of a perforated plate and gas generated on the electrode is withdrawn through openings of the perforated plate to the partition side.